Field of the Invention
The present invention relates to a honeycomb structure. More specifically, the present invention relates to a honeycomb structure, in which two or more cell structures are separated by a boundary wall, capable of relieving stress concentration generated near the boundary wall and preventing deterioration of a mechanical strength.
Description of the Related Art
Conventionally, in order to perform purifying processing of a harmful substance such as HC, CO, NOx or the like included in exhaust gas emitted from an engine of a vehicle or the like, a honeycomb structure loading a catalyst is used. Further, the honeycomb structure with an open end of a cell defined by porous partition walls subjected to plugging is also used as a filter for purifying the exhaust gas.
The honeycomb structure is formed as a pillar-shaped structure having partition walls which define a plurality of cells which functions as passages of the exhaust gas. Such a honeycomb structure has a cell structure in which the plurality of the cells is regularly arranged at a predetermined frequency on a plane perpendicular to a direction in which the cell is extended. Conventionally, one kind of the cell structure within the plane is arranged in one honeycomb structure, however in recent years, in order to improve purification efficiency of the exhaust gas or the like, a honeycomb structure having two or more kinds of the cell structures arranged within the plane is proposed. For example, a honeycomb structure provided with two or more kinds of the cell structures arranged within the plane by making a cell density or a cell shape different between in a center part and in a circumferential part within the plane perpendicular to the direction in which the cell is extended is proposed (for example, see Patent Documents 1 through 3).
[Patent Document 1] JP-A-2002-177794
[Patent Document 2] JP-A-2008-018370
[Patent Document 3] JP-A-2000-097019